Glossary
Sampler
The algorithm that turns random noise into a finished image step by step.
Samplers (DPM++ 2M Karras, Euler a, UniPC, etc.) are the numerical solvers that walk the diffusion model from pure noise to a final image. Different samplers produce subtly different aesthetics and need different step counts.
For most users the default sampler is correct. Switch only when you need a specific look or are optimising for fewer steps (speed).